[CentOS-virt] Slightly OT: FakeRaid or Software Raid

Manuel Wolfshant wolfy at nobugconsulting.ro
Thu Dec 3 01:34:19 UTC 2009

On 12/03/2009 03:08 AM, Grant McWilliams wrote:
>     Personally, I never touch raid5, but then, I'm on sata.   I do agree
>     that there are benifits to hardware raid with battery backed cache if
>     you do use raid5 (but I think raid5 is usually a mistake, unless it's
>     all read only, in which case you are better off using main memory for
>     cache.  you are trading away small write performance to get space;
>      with
>     disk, space is cheap and performance is expensive, so personally, if
>     I'm going to trade I will trade in the other direction.)
> Interesting thoughts on raid5 although I doubt many would agree. I 
> don't see how the drive
> type has ANYTHING to do with the RAID level. There are different RAID 
> levels for different situations
> I guess but a RAID 10  (or 0+1) will never reach the write or read 
> performance 
> <http://www.tomshardware.com/reviews/external-raid-storage,1922-9.html> 
> of a RAID-5. The disk space waste
> isn't too much of a problem anymore because as you say drives are 
> getting much cheaper. Although on that subject
> I'll mention that enterprise drives and desktop drives are NOT the 
> same thing. We deal in hundreds of drives and see
> about a 3% failure on desktop drives and only a fraction of that on 
> enterprise drives.
> I will say though that in my opinion the one really important thing to 
> consider is the price. These controllers
> aren't cheap and if you skimp you will pay. For sequential single 
> reads (streaming one stream) I'd consider
> using a software "RAID" 0. For a mirror I'd consider Software RAID but 
> once I get serious and go for RAID5 or RAID6 I'd
> only use Hardware RAID.
and none of this options is the answer to the problem "FakeRaid or 
Software Raid" :))

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